The present invention relates generally to telescoping, hydraulic power cylinders of the multi-section type. More particularly, the present invention is directed to a multi-section, triple action hydraulic cylinder assembly wherein, at the option of the operator, various smaller diameter internal coaxial tubes may be extended "out of order" in an effort to speed up the necessary sweep cycle.
In the prior art telescoping hydraulic cylinders are well known. A typical prior art hydraulic system comprises a major outer cylinder casing having a plurality of coaxially arranged, internally disposed, properly valved and dimensioned cooperating elements which will controllably extend outwardly of the main body. In normal operation high pressure oil is directed into the casing, and in response thereto, during the extension cycle, the next larger diameter portion of the hydraulic ram will be forced outwardly of the casing so as to effectuate compression. Once the next larger diameter cylinder portion extends outwardly from the base or casing, the end of which is usually fixed, then the next larger rod will extend outwardly, depending upon the hydraulic input controls as selected by the operator.
Thus to effectuate full extension of the cylinder, one must normally wait until the larger diameter cylinders are forced out of the casing, and until each of the progressively smaller diameter cylinders are similarly displaced until full extension is achieved. Normally the process is reversed in the retraction cycle. Conventional operation of such telescoping cylinders thus mandates the pumping of a maximum amount of oil in order to deflect the first stage. If only partial extension of the cylinder is required then it would be desirable to provide a means whereby the lowest diameter internal sections could be first extended, whereby a minimum quantity of oil need be pumped into the cylinder, in order to achieve the benefit of speed.
Such benefits would be particularly advantageous in conjunction with the "sweep cycle" of conventional refuse collection trucks. Such garbage trucks include front loaders which are adapted to be coupled to large metallic conventional cubical refuse containers for overhead dumping. Typical equipment is manufactured by Dempster, E-Z Pack, Hile and other manufacturers. Because the entrance door for dumping the garbage is located on the top of the truck right next to the cabin, once the refuse container is unloaded into the truck the hydraulic cylinder must sweep the garbage away from the initial position immediately below the overhead entrance door to make room for the next input of garbage. This is the so called "sweep" cycle wherein it is necessary to at least partially extend the operative cylinders so as to make room for the next load.
The same cylinder used for this sweep cycle is conventionally employed for the compression stroke, whereupon a platen compresses the load towards the rear exit door of the truck to compact the load during transportation. It is normal that the larger stages move first, and since these stages take the most of hydraulic oil, the time for extending the cylinders during this "sweep" is normally between Thirty Five to Forty Seconds.
It would thus seem desirable to provide a means within a heavy duty, elongated multi-section telescoping hydraulic ram which will facilitate independent selection of smaller internal sections so as to reduce the time for directing hydraulic fluid in the sweep cycle state. In other words, it is advantageous to provide a system wherein the smaller diameter sections of a multi-section, telescoped hydraulic cylinder may be operated independently of the larger diameter sections, while preserving operational integrity and preventing interference with other extension functions. Moreover, trouble free operation within the desired extension and retraction environment is required.
Within the prior art a variety of telescoping hydraulic cylinders are known. For example, attention is directed to U.S. Pat. No. 3,696,712, issued Oct. 10, 1972 which discloses a multi-sectioned hydraulic ram. Similar construction is seen in U.S. Pat. No. 3,934,423, issued Jan. 27, 1976, and U.S. Pat. No. 3,136,221, issued Oct. 27, 1961. An early multi-section hydraulic cylinder including a plurality of coaxially related independently operable elements is seen in U.S. Pat. No. 2,783,744. U.S. Pat. No. 3,610,100 is similar to the latter device.
U.S. Pat. No. 2,800,234 discloses a hydraulic system within the environment of a garbage truck vehicle body for packing refuse loads. The latter patent discusses in detail the particular problems which I have likewise addressed with my present invention. The closest prior art to me comprises U.S. Pat. No. 3,128,674 issued Apr. 14, 1964. In the latter system, however, the "triple action" attributes of the present design are lacking.
Hence I have provided a unique system which may be controlled by the user so as to provide all of the conventional benefits achieved by conventional telescoping multi-sectioned cylinders, while providing the benefits of double action and cooperative integrity of the various cylinders.
Moreover, I have provided an option to independently operate, either through an extension or retraction cycle, the smaller diameter sections of the cylinder in a triple action mode without depressurizing the larger diameter sections of the cylinder. In this fashion many advantages are realized, in that the hydraulic control and valve systems which must be employed to control my invention are simplified, integrity and reliability is increased, and, most importantly, speed in the sweep cycle for conventional refuse compacting and hauling garbage trucks is greatly enhanced.